Abstract
Multipe forms (D-I and D-II) of GTP cylcohydrolase, the first enzyme in pteridine biosynthesis, was demonstrated in Serratia indica by DEAE-cellulose chromatography. D-II was purified homogeneously. D-I contained small amounts of inactive protein. Both molecular weights were estimated to be 200000. D-II consisted of 8 subunits with the same molecular weight of 25000. The Km values (Km1 and Km2) for GTP were 3.2μM and 0.61μM for D-I, and 0.44μM and 5.5μM for D-II, respectively. Bivalent cations (Cu2+, Cd2+, Hg2+) inhibited the enzymes. Univalent cations (K+, Na+ and Li+) activated the enzymes.
